juanrga Posted April 24, 2012 Posted April 24, 2012 (edited) Karl Popper would like to have a word with you. Experimental confirmation means a theory has been tested to be valid in one particular set of circumstances. There is no logical guarantee that it will be correct anywhere else, to any arbitrary level of precision. There is no logical way to demonstrate that a theory is always correct under any circumstance, and so I don't think you can conclude that theories "cannot be wrong." The problem with Popper is that he was not aware that scientific theories are not universally applicable but have associated a field of applicability. When you verify a theory for a given kind of systems you are certifying that the theory is valid under those circumstances. When you find a system which cannot be described by the theory, this does not invalidate the theory but limits the scope of the theory to the previously verified systems. In fact, when you develop a new theory, you must check that the new theory contains to the previous theory as a particular case. E.g., Newtonian theory is not wrong and this is the reason which astronomers continue using it today (for the kind of systems within its scope) for explaining observations and for doing new predictions. I recall a recent issue in some journal with scientists criticizing the views of Popper and other philosophers about science, but I cannot find it now. Only ONE editor used the term "obsolete" Some other editor wrote: from the same talk page. I'd like to get some confirmation (or infirmation) from other knowledgeable members. Also the particular wiki article has been peer reviewed, and the word "obsolete" does not appear once on the main page. from the talk page introduction. One editor wrote the term obsolete, a second editor partially agreed with him, and a third confirmed the main argument of the first: modern formulations of QM do not use duality. Moreover, I also stated that I agree on that duality is obsolete and gave both technical reasons and references. The same Wikipedia explains that their 'peer-review' It is not academic peer review by a group of experts in a particular subject, and articles that undergo this process should not be assumed to have greater authority than any other. And a look to their archived 'peer-review' reveals that several editors noticed their disagreement with parts of the article, which still remain in the current version. So what? Edited April 24, 2012 by juanrga
swansont Posted April 24, 2012 Posted April 24, 2012 The associate dean of our college, a particle physicist, dedicates a week or two in his introductory modern physics course to the idea of wave-particle duality. I wouldn't say nobody serious uses the term "wave-particle duality" any more. I think there's a very important distinction to make between what gets taught and what gets used, and by whom. Wave functions and wave-particle duality certainly gets taught. Even if it's not used by those who ultimately go on and do particle physics for a living. (Which I can neither confirm nor deny, since I don't do particle physics) However, regardless of what gets used by those on the cutting edge of physics, it's hardly a useful distinction to make when discussing the concepts with someone who has a different background, e.g. someone who has never heard of the Klein-Gordon equation. 1
esbo Posted April 24, 2012 Posted April 24, 2012 That is not a correct approach to scientific theories. A scientific theory is something which has been experimentally confirmed [*], therefore it cannot be wrong. [*] Yes I know that currently some physicists and cosmologists abuse of the term and name "theories" to certain pseudo-philosophical speculations and hypothesis. Well what happens is they do an experiment and then come up with a theory to explain what is happening, however that does not mean the theory is correct just that it seems to explain what is happening. Often however the theory turns out to be wrong when further experiments are done, as happened with a lot of classical physics being out dated by all this relativity stuff. I mean there is all sorts of stuff which has been over turned by new developments. I recall one physicist saying "well this theory has been around for 100 years now so we can be fairly confident it is correct!!" (I forget what he was talking about). However I think he needs to recognise that in the past there were theories which had been around for thousands of years before they turned out to be wrong!!
Royston Posted April 24, 2012 Posted April 24, 2012 (edited) I think there's a very important distinction to make between what gets taught and what gets used, and by whom. Wave functions and wave-particle duality certainly gets taught. Even if it's not used by those who ultimately go on and do particle physics for a living. (Which I can neither confirm nor deny, since I don't do particle physics) However, regardless of what gets used by those on the cutting edge of physics, it's hardly a useful distinction to make when discussing the concepts with someone who has a different background, e.g. someone who has never heard of the Klein-Gordon equation. Precisely, and this seems to be what's causing confusion in this thread. You can't make the transition from classical physics to quantum physics without covering wave functions, and it's natural for a student (like myself) to insist on an interpretation when making that transition e.g wave-particle duality. You need to understand wave functions and the Schrodinger equation, before you move onto the Dirac equation, which you need to understand before moving onto path integrals, and so on and so forth. There's been a number of times whilst I've been studying, where an equation pops up, that may have some quantum property e.g spin. I remember learning about chemical potential in the context of helium burning, and spin was described as angular momentum around a centre of mass. That isn't how spin should be interpreted as, but, it would be a massive diversion branching off into the true properties of spin. It is inevitable when learning science, that there will be concepts that need to abandoned as you advance, but those concepts are a crucial part of reaching those advanced stages. Edited April 24, 2012 by Royston
questionposter Posted April 25, 2012 Posted April 25, 2012 I think there's a very important distinction to make between what gets taught and what gets used, and by whom. Wave functions and wave-particle duality certainly gets taught. Even if it's not used by those who ultimately go on and do particle physics for a living. (Which I can neither confirm nor deny, since I don't do particle physics) However, regardless of what gets used by those on the cutting edge of physics, it's hardly a useful distinction to make when discussing the concepts with someone who has a different background, e.g. someone who has never heard of the Klein-Gordon equation. A lot of the matrix and non-wave math Heisenberg developed for quantum mechanics in the end was the same as Schrodinger's wave mechanics, they had a sort of bitter feud over which one was right, and in the end they both got the same results.
juanrga Posted April 25, 2012 Posted April 25, 2012 The associate dean of our college, a particle physicist, dedicates a week or two in his introductory modern physics course to the idea of wave-particle duality. I wouldn't say nobody serious uses the term "wave-particle duality" any more. As explained before in this thread (Wiki-editors post similar thoughts in the talk page linked) duality is still used in introductory, historical, and non-rigorous treatments. E.g. Weinberg cites both duality and wave mechanics in the chapter 1 "Historical introduction" of the first volume of his textbook on QFT. But then in the chapter 2 "Relativistic Quantum Mechanics" he never mentions or use wave mechanics neither duality. Cohen in the first volume of his QM, discuss wave-functions and duality in the introductory chapter. Then in posterior chapters dealing with the serious stuff warns readers that not all quantum systems can be described by wavefunctions and then go to the generalized formalism. The Chapter 6 of Volume 1 of the Handbook on molecular physics and quantum chemistry gives an introduction to wave-particle duality. Then write: Although the coexistence of wave and particle properties now seem more acceptable, since the idea appears to resolve more difficulties than it creates, the question might still be asked: are photons and electrons really wave or [classical] particles? The answer must be that they are neither: they are quantum particles that behave like classical particles under some conditions and like [classical] waves under others There exists a well-known article published in FOP that devotes an entire section to explain why wave-particle duality is a myth and would be abandoned. The problem is that some of his arguments are wrong and other would only confound to some people here and for this reason I have not cited it. Well what happens is they do an experiment and then come up with a theory to explain what is happening, however that does not mean the theory is correct just that it seems to explain what is happening. Often however the theory turns out to be wrong when further experiments are done, as happened with a lot of classical physics being out dated by all this relativity stuff. I mean there is all sorts of stuff which has been over turned by new developments. I recall one physicist saying "well this theory has been around for 100 years now so we can be fairly confident it is correct!!" (I forget what he was talking about). However I think he needs to recognise that in the past there were theories which had been around for thousands of years before they turned out to be wrong!! The verified theories are not wrong when further experiments are done. They already were verified. That is the reason which classical physics continue being used today and works so well (for the kind of systems to which it apply) as 300 years ago. Relativity contains the classical stuff as a particular case.
questionposter Posted April 25, 2012 Posted April 25, 2012 (edited) As explained before in this thread (Wiki-editors post similar thoughts in the talk page linked) duality is still used in introductory, historical, and non-rigorous treatments. E.g. Weinberg cites both duality and wave mechanics in the chapter 1 "Historical introduction" of the first volume of his textbook on QFT. But then in the chapter 2 "Relativistic Quantum Mechanics" he never mentions or use wave mechanics neither duality. Cohen in the first volume of his QM, discuss wave-functions and duality in the introductory chapter. Then in posterior chapters dealing with the serious stuff warns readers that not all quantum systems can be described by wavefunctions and then go to the generalized formalism. The Chapter 6 of Volume 1 of the Handbook on molecular physics and quantum chemistry gives an introduction to wave-particle duality. Then write: There exists a well-known article published in FOP that devotes an entire section to explain why wave-particle duality is a myth and would be abandoned. The problem is that some of his arguments are wrong and other would only confound to some people here and for this reason I have not cited it. The verified theories are not wrong when further experiments are done. They already were verified. That is the reason which classical physics continue being used today and works so well (for the kind of systems to which it apply) as 300 years ago. Relativity contains the classical stuff as a particular case. Not all systems can be described as wave functions, but not all systems can be described as little spheres or with simple matrices either, that's why we have different theories. And as I already said, there is a lot of lol-wave math that is equivalent to quantum wave mechanics, like the uncertainty principal for instance. Heisenberg said the more precise the position, the less precise the momentum, and Schrodinger said you create a summation of multiple probable frequencies, both instances give the same result. Edited April 25, 2012 by questionposter
swansont Posted April 25, 2012 Posted April 25, 2012 As explained before in this thread (Wiki-editors post similar thoughts in the talk page linked) duality is still used in introductory, historical, and non-rigorous treatments. E.g. Weinberg cites both duality and wave mechanics in the chapter 1 "Historical introduction" of the first volume of his textbook on QFT. But then in the chapter 2 "Relativistic Quantum Mechanics" he never mentions or use wave mechanics neither duality. Which is precisely why you must have the caveat in the claim. The wave-particle duality is an outdated concept for people who do advanced physics for a living. It's no different than in any other part of physics — what you learn early on is merely an approximation of some more interesting details you learn later. But of you were to look at areas of science and of physics and advance physics, I think you'll get something that looks like a pyramid: there are more people who understand some science than who are reasonably well-versed in physics, and these yet outnumber those who might have studied relativistic QM or any other areas where wave-particle duality is recognized as being outmoded. This is not a situation where everyone has a physic degree, much less an advanced degree. It's not unlike chastising someone doing a physics 101 problem that Newtonian gravity is passé because of GR. Yes, it's true, but it's probably an utter failure when it comes to communicating any knowledge or even getting someone interested in learning the more advanced topic, and probably doesn't answer the question. If someone asks a question and their level of knowledge is wave-particle duality, then you answer the question at that level. Know your audience. (OTOH, if someone posts utter nonsense as if it were true, I think one should feel free to go all-in in destroying their argument)
Xittenn Posted April 25, 2012 Posted April 25, 2012 (edited) @juanrga I'm really interested in the OP, as it is stuff that I'm focusing my efforts toward. You have brought up an excellent point, one that I will be spending some time on in getting to understanding it. I think I've already said this, and if I missed a reply addressing it I'm sorry, but again, how might this be important to the behaviour of electron orbits? Also, do you have any interesting points to add about the OP? I would love to hear them, whether they are using dated methods of observation or not, as long as they convey a finer point. I know you are adamant about the idea you are trying to get across, as I've seen your same arguments elsewhere--will refrain from pointing at them. But, they are only useful in the context if they reveal something relevant to the conversation, which I'm literally dying to hear. I would prefer not wait four years until a teacher elaborates on them in a lecture! Edited April 25, 2012 by Xittenn
juanrga Posted April 25, 2012 Posted April 25, 2012 Which is precisely why you must have the caveat in the claim. The wave-particle duality is an outdated concept for people who do advanced physics for a living. It's no different than in any other part of physics — what you learn early on is merely an approximation of some more interesting details you learn later. But of you were to look at areas of science and of physics and advance physics, I think you'll get something that looks like a pyramid: there are more people who understand some science than who are reasonably well-versed in physics, and these yet outnumber those who might have studied relativistic QM or any other areas where wave-particle duality is recognized as being outmoded. This is not a situation where everyone has a physic degree, much less an advanced degree. It's not unlike chastising someone doing a physics 101 problem that Newtonian gravity is passé because of GR. Yes, it's true, but it's probably an utter failure when it comes to communicating any knowledge or even getting someone interested in learning the more advanced topic, and probably doesn't answer the question. If someone asks a question and their level of knowledge is wave-particle duality, then you answer the question at that level. Know your audience. (OTOH, if someone posts utter nonsense as if it were true, I think one should feel free to go all-in in destroying their argument) I understand your wise point. Thank you for sharing it. Please, let me state the mine. When being a student, I was tired of being said, "sorry what they said you, the past course, was not true". My didactic approach is different. I agree on that you must adapt your teaching level to the student level. But I do not think that one would be teaching stuff which is simply untrue [*]. Particularly, I find no reason for the outdated concept of duality and I am not the first who propose that it would be eliminated from textbooks. Duality is not really needed for explaining anything even at the basic level of the Schrödinger formulation, and of course it makes no sense in more advanced formulations of QM, not even as approximation. Why then introduce it in the first place? A wiki-editor noted the analogy of the wave-particle duality with the concept of relativistic mass. Relativistic masses play no role in fundamental physics, but they are used in very old textbooks of the 60s and in some recent introductory textbooks. My experience is that relativistic mass only adds confusion to students. There is a fierce debate with some physicists claiming for the elimination of this concept from textbooks and other claiming the contrary. Regarding the wave-particle duality concept the author of the FOP paper that I alluded in a previous post writes: In introductory textbooks on QM, as well as in popular texts on QM, a conceptually strange character of QM is often verbalized in terms of wave-particle duality. According to this duality, fundamental microscopic objects such as electrons and photons are neither pure particles nor pure waves, but both waves and particles. Or more precisely, in some conditions they behave as waves, while in other conditions they behave as particles. However, in more advanced and technical textbooks on QM, the wave-particle duality is rarely mentioned. [...] But why then the wave-particle duality is so often mentioned? One reason is philosophical; the word “duality” sounds very “deep” and “mysterious” from a philosophical point of view, and some physicists obviously like it, despite the fact that a dual picture is not supported by the usual technical formulation of QM. Another reason is historical; in early days of QM, it was an experimental fact that electrons and photons sometimes behave as particles and sometimes as waves, so a dual interpretation was perhaps natural at that time when quantum theory was not yet well understood. From above, one may conclude that the notion of “wave-particle duality” should be completely removed from a modern talk on QM. I agree with all of this, although I strongly disagree with many what he says in the same work about waves and particles and other QM stuff. Moreover, you assume that the student will take a more advanced course in future. But in my experience, most students take some introductory course in some discipline, never take a more advanced course and then believe that the stuff that was said to them would be taken as Divine Truth. Precisely, what I did when posted here was to correct to another poster who apparently believes that what he says is always true. Maybe my didactical approach is unrealistic or completely wrong. But I wait that it can be at least useful for those students who as myself hate the "sorry what they said you..." [*] I am not objecting to stuff which can be valid as approximation. E.g. Newtonian gravity can be taught today because it is an approximation to a more general theory of gravity and can be used to explain/predict phenomena. Number Pi can be approximated as 3.1416. Neither I am objecting to stuff said in chapters dealing with the history of the subject.
swansont Posted April 25, 2012 Posted April 25, 2012 Regarding the wave-particle duality concept the author of the FOP paper that I alluded in a previous post writes Perhaps you would share the paper's title and author rather than just alluding to it. Moreover, you assume that the student will take a more advanced course in future. Not at all. I wasn't referring to students as much as people participating on this forum. I am assuming they aren't going to go out and take a university class or three to pick up the additional knowledge. Their background may only be freshman physics and some pop-sci books.
juanrga Posted April 25, 2012 Posted April 25, 2012 @juanrga I'm really interested in the OP, as it is stuff that I'm focusing my efforts toward. You have brought up an excellent point, one that I will be spending some time on in getting to understanding it. I think I've already said this, and if I missed a reply addressing it I'm sorry, but again, how might this be important to the behaviour of electron orbits? Also, do you have any interesting points to add about the OP? I would love to hear them, whether they are using dated methods of observation or not, as long as they convey a finer point. I know you are adamant about the idea you are trying to get across, as I've seen your same arguments elsewhere--will refrain from pointing at them. But, they are only useful in the context if they reveal something relevant to the conversation, which I'm literally dying to hear. I would prefer not wait four years until a teacher elaborates on them in a lecture! The problem with the OP is that he is asking for details of an obsolete model which is not even valid as approximation. You can obtain the Schrödinger formulation of QM as approximation to a more general formulation. Indeed, there are atoms which are well-described by the Schrödinger equation, whereas others are not. But you cannot obtain what the OP has in mind as an approximation to QM, because the 'planetary model' of the atom is non-physical. None atom of the periodic table can be described by the 'planetary model'. Sorry, but the concept of electron orbits does not exist neither in the theory of QM nor in the lab! Adequate answers to the OP are given in the responses from #2 to #5 including the mine. Perhaps you would share the paper's title and author rather than just alluding to it. http://www.springerlink.com/content/71rp68556843238n/?MUD=MP The abstract is here http://www.springerlink.com/content/71RP68556843238N/primary I agree with many of what he says but disagree on other aspects. E.g. I agree on that duality is a myth, but disagree with his Bohmian approach to waves. Some of his claims are shown incorrect in standard textbooks (Weinberg, Cohen...). I think that this is a good reference for people who already knows QM, otherwise it can be a confusing reference. Therefore use it at your own risk
Xittenn Posted April 25, 2012 Posted April 25, 2012 @juanrga Neither post says much about what is actually happening, more so they focus on what is not happening. As far as I've understood for quite some time now QM is approached 'historically' as a wavefunction, but this isn't to say as an orbital model. I've had it in my head that once we move forward from Bohr's model we observe electron orbits as a transverse standing wave and then we continue to move from there. The best that I can get about the observed properties of an electron orbit are that they have 0 classical orbital angular momentum, >0 velocity, and although they have spin angular momentum the spin angular momentum is again not analogous to classical angular momentum. Some comments have lead me prior to making statements like "electrons are a standing wave with probabilities of density that see such densities popping in and out of existence through time . . . . " Prior suggestions have inconclusively concluded that charge itself is not quantized, although what we observe is quantized charge. Can you add to these statements or modify them so that they are the most correct?
Xittenn Posted April 25, 2012 Posted April 25, 2012 Well, I think that I already explained why "wave mechanics" is a misnomer, there is none wave, which is the historical origin for this misnaming, and why "wave mechanics" gives only an approximated description (i.e. it is far from being fundamental). Regarding your other claims, an operator does not "generate numbers", but gives the observable (mass is not a number, energy is not a number...). When scientists write something as H |Psi> = E |Psi>, with H the Hamiltonian operator, the E is not a number but a physical quantity. I have not checked the entire thread, but in #19 you wrote that "electrons are waves". Even without the "only", what you said in #19 was not true. The paper really contradicts the statement above, but it makes sense of a lot of the ideas that juangrga has presented. From my interpretation of what I am reading electrons are waves exclusively until measured where this collapses the wave equation to have a definite wave packet or 'particle.' If Kets are working with measured particle systems I could see why we would drop the notion of the wave. I have heard the statement before that electrons are in reality exclusively waves, and this is the first time that I've ever heard mention that they are not, that they are simply particles. If charge is not quantized I would have a hard time accepting the postulate that electrons are particles, and not waves that when measured have definitive location--insert HUP somewhere in there. Another statement I've heard echoed in this thread is that both Ket and wave interpretations fail to explain higher order particle systems, and electron movements between nuclei and quantum states. I wish I could do the math . . . . one day . . . :/
questionposter Posted April 25, 2012 Posted April 25, 2012 (edited) It seems like every theory in just the QM world alone as it's drawbacks and things it fails to describe. With that said, why do scientists think its a good idea to try and force relativity into it? Edited April 25, 2012 by questionposter
swansont Posted April 26, 2012 Posted April 26, 2012 It seems like every theory in just the QM world alone as it's drawbacks and things it fails to describe. With that said, why do scientists think its a good idea to try and force relativity into it? Because relativity has consequences, for which one must account.
juanrga Posted April 26, 2012 Posted April 26, 2012 (edited) The paper really contradicts the statement above, but it makes sense of a lot of the ideas that juangrga has presented. From my interpretation of what I am reading electrons are waves exclusively until measured where this collapses the wave equation to have a definite wave packet or 'particle.' If Kets are working with measured particle systems I could see why we would drop the notion of the wave. I have heard the statement before that electrons are in reality exclusively waves, and this is the first time that I've ever heard mention that they are not, that they are simply particles. If charge is not quantized I would have a hard time accepting the postulate that electrons are particles, and not waves that when measured have definitive location--insert HUP somewhere in there. Another statement I've heard echoed in this thread is that both Ket and wave interpretations fail to explain higher order particle systems, and electron movements between nuclei and quantum states. I wish I could do the math . . . . one day . . . :/ This is why I was reluctant to cite that paper, although it correctly points that wave-particle duality has only historical interest and is not used in any modern and rigorous presentation of QM, it contains ideas that are simply plain wrong. In #87 I wrote about this paper: I agree with many of what he says but disagree on other aspects. E.g. I agree on that duality is a myth, but disagree with his Bohmian approach to waves. Some of his claims are shown incorrect in standard textbooks (Weinberg, Cohen...). I think that this is a good reference for people who already knows QM, otherwise it can be a confusing reference. Therefore use it at your own risk The idea of that particles are waves is plain wrong. That is the reason which particle physics is not named "wave physics". And this is also why an electron is considered an "elementary particle" and not an "elementary wave". Standard textbooks in QM and QFT as Weinberg, Cohen, Mandl and Shaw... explain why it is not true that a particle was associated to a wavefunction. Weinberg emphasizes that what we measure in the lab are particles. If my memory does not fail, yourself quoted part of a textbook emphasizing that solutions to Klein-Gordon equation are not wavefunctions! I apologize for citing that paper when swansont asked. Although it seems that it settled out that duality is an outdated concept it has generated other doubts . Edited April 26, 2012 by juanrga
Xittenn Posted April 27, 2012 Posted April 27, 2012 Yes, I did quote from Ryder's QFT, but is particle physics QM or a subset of QM? How is charge defined under QFT? Honestly, I will need to review much more literature before I can accept any conclusion on this matter, there is currently insufficient data, and too much controversy. Maybe I will understand a little better when I've done some work with Noether's Theorem, and more on waves in year two physics courses. Currently you are the only one who has made these complete statements because I can see how Ryder's statements fit with the paper, but I don't find any statements that are exactly equivalent to yours. The outcome of your posts over the internet doesn't help matters much either! As I stand the matter is inconclusive, but thanks again for pointing the matter out to me, I'm sure we all gained some insight from your posts. d b 2
juanrga Posted April 27, 2012 Posted April 27, 2012 (edited) Yes, I did quote from Ryder's QFT, but is particle physics QM or a subset of QM? How is charge defined under QFT? Honestly, I will need to review much more literature before I can accept any conclusion on this matter, there is currently insufficient data, and too much controversy. Maybe I will understand a little better when I've done some work with Noether's Theorem, and more on waves in year two physics courses. Currently you are the only one who has made these complete statements because I can see how Ryder's statements fit with the paper, but I don't find any statements that are exactly equivalent to yours. The outcome of your posts over the internet doesn't help matters much either! As I stand the matter is inconclusive, but thanks again for pointing the matter out to me, I'm sure we all gained some insight from your posts. d b Particle physics is based in QM, but does not use the old wave formulation of QM. Modern and advanced treatises on QM do not use the old wave-function approach. The wave-function approach is still given in introductory courses to QM, which only deal with simplest problems; whereas more advanced treatises on QM deal with the old wave-function approach only in the chapter dealing with the history of QM. The old wave-function approach is not abandoned by aesthetic or philosophical reasons. It happens that quantum particles cannot be always described by wavefunctions. People who only takes an introductory course in QM seems the believe the contrary. I already cited three or four standard books in QM and QFT giving the details of all that I am saying here. Consider the textbook by Cohen. The volume 1 starts with a historical introduction that deals with older experiments, the old wave-function approach, the old duality concept, and all that. But then in chapter II, which is a kind of interlude for the rest of the material in the volume, adds [bold emphasis is from mine]: Actually, the introduction of state vectors and the state space does more than merely simplifying the formalism. It also permits a generalization of the formalism. Indeed, there exists physical systems whose quantum descriptions cannot be given by a wave function: we shall see in chapters IV and IX that this is the case when the spin degrees of freedom are taken into account, even for a single particle. As I already emphasized, more than one time, a particle cannot be a wave or behave as a wave. First, this wave-particle-duality-nonsense (Nickolic names it "myth") is traced to an old confusion between the quantum system under study (aka the particle) with its mechanical state in the wave-function formulation (aka the wavefunction). Second there are experimental situations where the state of a particle is not given by a wavefunction. Or said in another equivalent form: there experimental situations where the observables of a particle cannot be described using wavefunctions. Some examples of systems whose quantum state is not given by a wavefunction include: A single isolated stable particle when one takes into account spin (see quote above). A Klein-Gordon particle (see Ryder's). An electron in a multi-electronic atom. Due to electron-electron correlation (see previous posts from mine). An unstable particle. Unstable states are not describable by wavefunctions (see the Adv. Chem. Phys. paper por details) Etc. Finally I want emphasize that I do not find a "too much controversy". Some aspects of QM are still under debate by the experts, but others are not. It happens that QM is a technical and complex subject and some authors are more prone to error that others. I do not know what you mean by "How is charge defined under QFT?" Charge is not defined, but is one fundamental physical quantity, which is measured in the lab. E.g. the charge of an electron is e and its value is given in tables of constants. Edited April 27, 2012 by juanrga
questionposter Posted April 27, 2012 Posted April 27, 2012 (edited) Because relativity has consequences, for which one must account. But couldn't there be some new extra-dimensional theory that describes a way in which the manifolds of space fold as to create different dilations? Particle physics is based in QM, but does not use the old wave formulation of QM. Modern and advanced treatises on QM do not use the old wave-function approach. The wave-function approach is still given in introductory courses to QM, which only deal with simplest problems; whereas more advanced treatises on QM deal with the old wave-function approach only in the chapter dealing with the history of QM. The old wave-function approach is not abandoned by aesthetic or philosophical reasons. It happens that quantum particles cannot be always described by wavefunctions. People who only takes an introductory course in QM seems the believe the contrary. I already cited three or four standard books in QM and QFT giving the details of all that I am saying here. Consider the textbook by Cohen. The volume 1 starts with a historical introduction that deals with older experiments, the old wave-function approach, the old duality concept, and all that. But then in chapter II, which is a kind of interlude for the rest of the material in the volume, adds [bold emphasis is from mine]: As I already emphasized, more than one time, a particle cannot be a wave or behave as a wave. First, this wave-particle-duality-nonsense (Nickolic names it "myth") is traced to an old confusion between the quantum system under study (aka the particle) with its mechanical state in the wave-function formulation (aka the wavefunction). Second there are experimental situations where the state of a particle is not given by a wavefunction. Or said in another equivalent form: there experimental situations where the observables of a particle cannot be described using wavefunctions. Some examples of systems whose quantum state is not given by a wavefunction include: A single isolated stable particle when one takes into account spin (see quote above). A Klein-Gordon particle (see Ryder's). An electron in a multi-electronic atom. Due to electron-electron correlation (see previous posts from mine). An unstable particle. Unstable states are not describable by wavefunctions (see the Adv. Chem. Phys. paper por details) Etc. Finally I want emphasize that I do not find a "too much controversy". Some aspects of QM are still under debate by the experts, but others are not. It happens that QM is a technical and complex subject and some authors are more prone to error that others. I do not know what you mean by "How is charge defined under QFT?" Charge is not defined, but is one fundamental physical quantity, which is measured in the lab. E.g. the charge of an electron is e and its value is given in tables of constants. Just because wave mechanics isn't the only math doesn't mean it doesn't exist. By your reasoning I could agrue gravity doesn't exist because there are some situations where attraction can't be described by it, aka magnetism. Considering that much of Schrodinger's math and Heisenberg's math end up getting the exact same results, I'd say quantum wave mechanics is only "outdated" because there are simpler ways to state the patterns found in them, such as the "Heisenberg Uncertainty Principal". Edited April 27, 2012 by questionposter
swansont Posted April 27, 2012 Posted April 27, 2012 But couldn't there be some new extra-dimensional theory that describes a way in which the manifolds of space fold as to create different dilations? Could there be? Sure. But relativity is what is known. When you incorporate conjecture into your model, what you have is conjecture; it's only as strong as the weakest link. Relativity is not conjecture.
juanrga Posted April 27, 2012 Posted April 27, 2012 Just because wave mechanics isn't the only math doesn't mean it doesn't exist. By your reasoning I could agrue gravity doesn't exist because there are some situations where attraction can't be described by it, aka magnetism. Considering that much of Schrodinger's math and Heisenberg's math end up getting the exact same results, I'd say quantum wave mechanics is only "outdated" because there are simpler ways to state the patterns found in them, such as the "Heisenberg Uncertainty Principal". Nothing of this is related to what I have really said.
IM Egdall Posted April 27, 2012 Posted April 27, 2012 I am not an expert in quantum mechanics, so please feel free to educate me here. I thought there are two basic ways to model in quantum mechanics. In the first way, quantum field theory, a wave function travels from place to place. When an interaction occurs, the wave function collapses to a local wave packet of energy we can refer to as a particle. The wave function gives the probability of detecting this particle at a certain place and time. The second method, Quantum Electrodynamics (QED), models particles as single points. The sum of all paths method is used to determine the probability that the particle is detected at a given place at a certain time. The probability amplitudes for each possible path the particle could take are summed, then squared to compute this probability. There is no wave in QED. (Summing amplitudes from Feynman diagrams of interaction events and squaring is also a way to determine probability.) The first method uses waves and wave mechanics. The second uses particles and the sum of all paths. I think they both give equivalent results.
questionposter Posted April 28, 2012 Posted April 28, 2012 (edited) Nothing of this is related to what I have really said. No I'm pretty sure it's exactly related to what you said, that's why I quoted you, you said wave mechanics in quantum mechanics is a flat out wrong and a "myth", which I don't see how it could be a myth seeing as how it's documented that scientists to this day use to to achieve values of some things because of how well certain aspects of atoms can be described by it, like predicting molecular bonding. Also, aren't wave functions used with Dirac equations? And don't Dirac equations have problems too? http://en.wikipedia....i/Klein_paradox Edited April 28, 2012 by questionposter
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